JP4275628B2 - Furnace for heating a moving container blank of thermoplastic material - Google Patents

Abstract

The oven (1) has conveyors (2) to carry and move blanks, especially thermoplastic preforms or intermediate containers, passing in line on either side of heaters (3). Each conveyor has at least two parallel branches (4, 5) running close to one another in forward and reverse directions and connected by a loop (8) outside the oven's heating zone. A variant of the design has the conveyor made with two pairs of parallel branches passing on either side of the heaters, and two loops outside the heating zones. The oven's heaters are in the form of infrared lamps, with reflectors (9) on the opposite surfaces.

Description

  The present invention generally relates to the manufacture of containers such as bottles and flasks made from thermoplastic resins, such as PET and PEN, by blow molding or stretch blow molding from containers or blanks (semi-finished products or intermediate products of containers). In particular, the present invention relates to a method of heating a blank prior to a blow molding or stretch blow molding process so that the resin can be softened and deformed.

  More precisely, the present invention comprises a conveying means suitable for supporting and moving one after the other while rotating the blank about its axis, and a conveying means for heating the body of the moving blank. And a heating means arranged on the side of the machine, and in particular a furnace for superheating a moving blank, in particular a semi-finished product made of a thermoplastic resin or an intermediate product of a container.

  The entire thermoplastic must be heated to a temperature sufficient to be flexible so that the stretching process is performed accurately and uniformly across the blank body, which is the temperature at which the material is crystallized. It is necessary not to be too high in order to prevent the change. This means that a sufficient amount of heat (eg continuously generated by infrared radiation) is propagated through the entire thickness of the blank wall (eg the central part) despite the low thermal conductivity of the thermoplastic resin. It is heated up to).

  In the case of a heating means such as an infrared lamp, the purpose cannot be achieved even if the infrared transmission output is forcibly increased in order to achieve such a result more quickly. This is because the thermal conductivity of the thermoplastic resin is low, so that a certain amount of time is required to achieve the heating of the central part, and when trying to shorten this time by increasing the output of infrared radiation, This is because there is a risk of crystallizing the surface material of the outer surface. Therefore, such a solution must be abandoned.

  Therefore, this problem must be solved by increasing the time that the thermoplastic resin is exposed to the heating means.

  One possible solution is to reduce the speed of the blanks that pass through the heating means arranged on the side. However, it must also be noted that container manufacturers are constantly trying to increase the achievable productivity, especially by increasing machine speed. Therefore, such a requirement is contrary to reducing the moving speed of the production line at any point on the production line. Therefore, this solution must also be abandoned.

  While it is certainly conceivable to reduce the speed of blank movement through the furnace (eg, reduce the speed in half), having the two furnaces in parallel will maintain the overall throughput. However, this solution can be very expensive both in terms of equipment and energy and must be abandoned as well.

  A useful solution might be to increase the length of the furnace, but this would lead to an increase in irradiation time for a specific movement speed of the blank. Therefore, it is conceivable to reduce the transmission output of the heating means, but this is possible because there is sufficient time for heat to propagate through the thickness of the blank wall. Certainly, this solution involves the cost of the equipment to increase the length of the furnace, but this also reduces the energy required for heat treatment of the blank during use (up to 35%). It is clear that it is economical.

  However, this solution is generally beneficial for the reasons described above, but has the disadvantage that it is difficult to implement in practice because the furnace so provided is very long.

  Under these circumstances, the present invention proposes an improved solution that meets the requirement of exposing the blank to the heating means for a long time while avoiding the various drawbacks of the aforementioned solutions.

Conveying To this end, the present invention is a blank, respectively while rotating about its axis, and configured conveying means to move supporting one after another, to heat the body of the blank on the move Heating means arranged on the side of the means , the conveying means is configured to have at least two conveying branch portions extending in parallel with each other and having opposite conveying directions, and the plurality of blanks are one after another In a furnace in which the heating means is located between two parallel branch branches extending adjacent to each other , the heating means is located between the two branch branches. has a pair of infrared lamps arranged in, whereby these lamps, you simultaneously heated blanks moving the two conveying branch portion upper, respectively which opposition direction from two directions and it features a call Suggest that the furnace.

The two branch parts are located outside the area where the heating lamp operates and are therefore joined at one of their ends by a looped conveying part which constitutes a section in which the blank is thermally stabilized Is preferred.

  With this configuration, each blank passes through the furnace at least twice, and during these two heating steps corresponds to the path of rotation of the conveying means and constitutes a stabilization step in which heat continues to diffuse into the material. There is an interruption. Therefore, the heating time is doubled, and as a result, the thermoplastic resin is heat-treated under optimum conditions, and the entire resin is uniformly and quickly heated to the central portion.

From a structural point of view, the above-mentioned advantageous results are obtained with one combination of heating lamps , the effectiveness of which is that heating lamp radiation is used here in two directions and is no longer as in conventional furnaces. Doubled by not being direction.

  Furnace configurations in which two rows of moving objects are processed on each side of the heating means are certainly known (for example, EP 0 868 284 and DE 24 27 611). See). However, in these known configurations, the two rows of heated objects move in the same direction. Although these known furnaces can double the throughput, each object passes only once through the furnace. Therefore, the exposure time of each object does not increase with respect to the exposure time of an object passing through a conventional furnace of the same length (that is, a row of objects).

Furthermore, as recommended by the present invention, in a furnace having two opposite paths, each object is exposed twice to the heating lamp , resulting in a longer exposure time, It should be noted that advantageously, the power of the radiation emitted by the heating lamp is reduced, thus reducing the power consumption. This is particularly important for the user (tests have shown that savings of 50% or more can be achieved when using infrared lamps).

In one advantageous embodiment, the furnace has two pairs of parallel transfer branches, each having a heating lamp disposed between the two transfer branches of each pair, the four transfer branches. The parts are joined together by a looped conveying part located outside the area where the heating lamp operates. In order to make a small furnace, it is advantageous that the four transfer branches are parallel to each other, and these branches are generally straight.

It is preferable to provide a plurality of reflectors corresponding to the heating means by a method known per se, and these reflectors are provided on the side opposite to the side where the heating lamp is provided along each conveyance branch portion. Placed in.

  The present invention will be understood more clearly by reading the following detailed description of specific embodiments, which are presented as fully non-limiting examples.

  First, referring to FIG. 1, the furnace 1 is intended to heat a semi-finished product or a container intermediate product made of a thermoplastic, such as a moving blank, PET or PEN, Such a furnace can be installed especially upstream of the blow molding or stretch blow molding equipment for producing the container.

  The furnace 1 has transport means 2 suitable for supporting and moving blanks (not shown) one after the other while rotating about their axes. These transport means simultaneously support the blank at its neck so that each blank is moved and simultaneously exposed to the heating means 3 disposed on the side of the transport means over the entire outer periphery of the body. , Articulated with multiple supports ("spinners") suitable to be rotated (eg by engaging an attached toothed wheel with a fixed side chain or rack) The arrangement or chain itself may be constructed in a known manner.

  According to the invention, the conveying means 2 is configured such that at least two conveying branch portions 4, 5 are opposite in direction of movement, and at the same time, substantially parallel to each other and adjacent to each other.

  The blanks move one after the other (side by side) along the two branches 4, 5 as symbolized by the arrow 6.

  The heating means 3 is arranged between the two branch parts 4 and 5 of the transport means 2 and operates on both sides, and is moved in the opposite direction along each of the two branch parts 4 and 5 of the transport means Are simultaneously heated.

  As an example, FIG. 1 shows a heating means 3 here in the form of three consecutive sets 7 of infrared heating lamps.

In the preferred embodiment, as shown in FIG. 1, the two branch portions 4, 5 of the generally straight conveying means inside the furnace are connected to the loop of the conveying means at one end of the furnace 1 (right side in FIG. 1). The loop-shaped part 8 of the conveying means is connected to each other easily by the cylindrical part 8, in addition to the function of combining the branch parts 4, 5 penetrating the furnace into one, the heat is continuously thermoplastic. It also acts as a stabilization section that allows it to diffuse into the resin and prevents the outer surface of the blank body from being overheated.

  The furnace 1 is provided with a plurality of reflectors 9 arranged on the other side of the branch portions 4 and 5 of the conveying means toward the heating means 3 by a method known per se.

  In a furnace constructed according to the invention, each blank passes twice in succession against the heating means, with a thermal stabilization period in between. For a given length of furnace, the semi-finished product can be heated more uniformly and up to the central part, but the same heating time is obtained for each semi-finished product, so that one transport row is provided. Compared with a conventional furnace, without increasing the number of heating lamps and without extending the operating length of the furnace, the output of the heating means is greatly reduced, thereby greatly reducing the power consumption.

  FIG. 2 schematically shows a specific example of a furnace implementing the above configuration. In fact, the configuration shown in FIG. 1 is similar to the configuration shown in FIG. 1 (by parts A and B), so that the blank passes through the furnace four times in succession, so that 4 The continuous heating is performed with a thermal stabilization period interposed therebetween.

  The blank that has reached E is sent out by the feeding means 10 (for example, a feeding wheel) to the conveying means 2 comprising the loop-like chain 2 with the support closed. The chain 2 then enters part A of the furnace 1 from its branch part 4A, where the blank is subjected to a first heat treatment and then travels along the looped part 8A before the second part at the branch part 5A. Receive heat treatment.

  The blank then travels along the connecting part 11 which also defines the thermal stabilization section, where the blank is conveyed to the second part B of the furnace, where the blank is a similar path, i.e. the branch where the heating is carried out. Follow part 4B, loop part 8B where thermal stabilization is performed, and branch part 5B where heating is performed.

  When leaving the bifurcated part 5B, the part 12 transports the blank to a lowering means 13 (such as a "pick-up" wheel) where the blank is removed from the support of the chain 2 (this chain returns to the input means 10). For example, it is lowered at S towards a blow molding or stretch blow molding unit. Since the lowering means 13 is not directly adjacent to the furnace outlet, the portion 12 itself constitutes a thermal stabilization section that completes the diffusion of heat into the thermoplastic resin.

  The four branch portions 4A, 5A, 4B, and 5B may be parallel to each other so that a simple and small-sized furnace with little heat loss can be configured. Furthermore, a member common to the operation of these two parts A and B, in particular a fan for sending a gas for cooling the surface of the blank, may be arranged in the central part between the aforementioned parts A and B of the furnace. it can.

It is the simplified figure which shows the furnace structure which implements the structure of this invention. FIG. 2 is a simplified diagram illustrating an advantageous example of an embodiment of a furnace utilizing the configuration of FIG.

Claims (6)

Made of thermoplastic resin, a furnace for heating a plurality of blanks in the mobile (1), the blank, while rotating each about its axis and configured to move supported one after another and conveying means (2), have a heating means is arranged on the side (3) of the conveying means (2) for heating the body of the blank in the movement of the said conveying means (2) extends flat row to another, the conveying direction is configured to have at least two conveying branch portion opposite (4,5), said plurality of blanks is moved along said two branches parts one after another In the furnace (1) in which the heating means (3) is arranged between the two parallel transfer branches (4, 5) extending adjacent to each other, the heating means (3) A set of infrared rays placed between the two transfer branches Has a lamp, whereby these lamps is characterized and Turkey be heated simultaneously the blank is moving the two conveying branch portion upper, respectively which opposition direction from two directions furnace . The two transfer branch portions (4, 5) are joined at one of their ends by a loop-shaped transfer portion (8) located outside the region where the heating lamp operates. A furnace according to claim 1, characterized. Parallel conveying branch portion of the two pairs (4A, 5A; 4B, 5B ) has a heating lamp (3A, 3B) between the two branches portions of each pair are disposed, four conveying branch portion Furnace according to claim 1 or 2, characterized in that they are connected to each other by means of a loop-shaped conveying part (8A, 8B) located outside the region in which the heating lamp operates.   The furnace according to claim 3, characterized in that the four transfer branches (4A, 5A; 4B, 5B) are parallel to each other. Wherein both conveying branch portion (4,5) is characterized by a straight line, a furnace according to any one of claims 1 4. A plurality of reflectors (9) are arranged on the side of each branch part for conveyance on the side opposite to the side on which the heating lamp (3) is provided. The furnace according to any one of 5.

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